public class HomeWork13_02{
    public static void main(String[] args){
        String[] students = new String[]{
            "shxt_0712", "shxt_0704", "shxt_0715",
            "shxt_0504", "shxt_0602", "shxt_0711",
            "shxt_0607"
        };
        
        int count = StuCount.count(students, "shxt_07", 0);
        System.out.println(count);
    }
}

class StuCount{
    public static int count(String[] students, String sign, int index){
        int count = 0;
        for(String item : students){
            if(item.indexOf(sign, index) == 0){
                ++count;
            }
        }
        
        return count;
    }
}